1. Field of the Invention
This invention relates generally to solar cell modules. More particularly, this invention relates to an improved method for fabricating a solar cell module.
2. Background of the Invention
In general, a solar cell module consists of an array of individual solar cells electrically interconnected and housed in a protective and supporting enclosure.
Typically the individual solar cells of the module are arranged in columns and rows and are interconnected by flexible interconnector means which are positioned so as to connect the cells in the requisite series and/or parallel circuit arrangement. The circuit arrangement, of course, depends upon the desired output voltage and current at the module peak power point. Flexibility in the interconnectors permits slight movement of the individual cells in the array without breaking the electrical connections.
A protective enclosure or housing is used in order to protect the solar cells and the interconnecting means from degrading as a result of environmental conditions, such as humidity, pollutants, wind, snow and ice damage and the like. Typically the housing consists of a rigid support structure on which the solar cells are mounted and a top light transparent encapsulant through which solar radiation passes before impinging on the active solar cells. Frequently, a rigid light transparent top member, as added protection, also is provided since the encapsulant surface can be damages by animals, hail, etc. More recently there has been a tendency to employ an optically clear superstrate to not only protect the solar cell array against environmental hazards but also to serve as the structural support for the array. Obviously a solar cell array having a single material which serves both as a supporting surface and as a protective packaging material for the solar cells offers significant commercial advantages; however, bonding the solar cells to a rigid light transparent superstrate has not been without significant technical problems. For example, since the light transparent superstrate consists of a substantially flat planar sheet of rigid, light transparent, electrically nonconducting material, such as glass, an adhesive is required to mount an array of solar cells on the bottom surface of such a superstrate. For this purpose, electrically nonconductive, light transparent plastic resins such as silicone rubbers and the like, which are employed as encapsulants for all manner of electronic packages, are used as adhesives. As will be appreciated, the height of the electrodes on the top surface of each of the solar cells in the array can vary one from the other. The height of the interconnectors, as measured from the top surface of the solar cells, may vary also. Additionally, slight movement of encapsulated cells may occur during use of the module. Consequently, it is especially important to align the cells during encapsulation as uniformly as possible to avoid creation of stresses, especially where an electrode or interconnector may contact the superstrate. Top alignment of the cells and interconnectors has been virtually impossible in the past to achieve, and instead a considerable thickness of encapsulant is employed in bonding the solar cell array to the superstrate. Use of large amounts of encapsulate is costly. Additionally, it is absolutely necessary to assure that the encapsulant is free of air bubbles and the like which would tend to cause degradation of the module when exposed to solar energy.